The goal of this Career Development Award (K23) is to expand on the applicant's qualitative work on fathers in families and gain the theoretical, methodological, and intervention skills to understand young men's health during the transition to fatherhood and to devise ways to improve men's health. Compared to women, men have a shorter life expectancy, engage in more risky health behaviors, and underutilize recommended health services. However, the predominant conceptualizations of men's health in the United States are largely organ- based and often do not account for social and contextual factors. Though the majority of men are fathers, there is little knowledge about how the transition to fatherhood affects men's health, especially among young men. Men are known to attend their child's birth and are prepared to make life changes during the transition to fatherhood. The specific aims of this proposal are: 1) to examine the effect of the transition to fatherhood on young men's health and health behaviors, 2) to characterize healthcare utilization for young men during this transition and 3) using the information obtained in aims 1-2 and through focus groups, to design and pilot a randomized intervention using technology to promote young men's health during the transition to fatherhood. To examine these aims, the applicant presents a plan for formal and experiential training that was devised along with his four exceptional mentors (Drs. Greg Duncan, P. Lindsay Chase-Lansdale, David Cella, and Eric Whitaker) and noted fathering research expert Dr. Rebekah Levine Coley that will allow him to gain experience and skills in research methodology including survey design, longitudinal and cross-sectional analyses, the psychobiology of stress (including biomarker analyses), economics and decision making, theories of reproduction and fertility, and health communication including the use of technology. To examine aims 1 and 2, this proposal uses data from male participants in the National Longitudinal Study of Adolescent Health (Add Health) a longitudinal, nationally representative dataset that spans adolescence to early adulthood. Aims 1 and 2 use pre-post comparisons and point-in-time comparisons to examine differences between young men with children and those without, and then uses longitudinal methods to create a person-year dataset to examine the contribution of becoming a father to the outcomes. Selection issues are dealt with in a variety of ways, including building sibling models. Aim 3 expands on the above findings through focus groups with new fathers to determine the set of relevant health topics preferences for health information delivery. After pilot testing the delivery of health information via technology, a randomized intervention of 200 fathers will be conducted and changes to health and health behaviors will be evaluated. In sum, the goal of this proposal is to understand and improve the health, healthcare utilization, and longevity of young men, a historically difficult-to reach group.